JP6081831B2 - Honeycomb structure, honeycomb catalyst body using the same, and method for manufacturing honeycomb structure - Google Patents

Description

  The present invention relates to a honeycomb structure that supports a catalyst for exhaust gas purification, a honeycomb catalyst body using the honeycomb structure, and a method for manufacturing the honeycomb structure.

Exhaust gas discharged from internal combustion engines such as automobile engines contains harmful substances such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO _X ). Catalytic reactions are widely used to reduce such harmful substances and purify exhaust gas. In this catalytic reaction, it is possible to generate other harmless substances from harmful substances such as carbon monoxide (CO) by a simple means of contacting exhaust gas with the catalyst. Therefore, in automobiles and the like, it is common to purify exhaust gas by installing a catalyst in the middle of the exhaust system from the engine.

  When installing a catalyst in an exhaust system of an automobile or the like, a honeycomb catalyst body in which a catalyst is supported on a honeycomb structure is used. In the honeycomb catalyst body, a honeycomb structure (honeycomb structure) is formed by the partition walls supporting the catalyst, and each cell surrounded by the partition walls functions as an exhaust gas flow path. In such a honeycomb catalyst body, exhaust gas is divided into a plurality of cells, and the exhaust gas thus subdivided is brought into contact with the catalyst supported on the surfaces of the partition walls. Thus, in the honeycomb catalyst body, exhaust gas can be processed with high purification efficiency by simultaneously processing a plurality of exhaust gases.

  Furthermore, with regard to the honeycomb catalyst body, a technique has been proposed in which a honeycomb structure is formed by porous partition walls having innumerable pores, and the catalyst is supported on the inner wall surfaces of the partition wall pores (for example, Patent Document 1). ). In this technique, the catalyst loading in the honeycomb catalyst body is increased by loading the catalyst in the pores. Further, in this technique, the contact frequency between the exhaust gas and the catalyst is further increased by allowing the exhaust gas to flow into the pores of the partition walls and bringing the exhaust gas and the catalyst into contact with each other even in the pores.

JP 2009-154148 A

  However, in the above honeycomb catalyst body, it is possible to increase the amount of the catalyst supported by supporting the catalyst in the pores, but it is impossible to effectively function the catalyst supported in the pores. There is. In the above honeycomb catalyst body, the pores may be blocked by the catalyst, or the pore openings on the partition wall surface may be narrowed. Therefore, in the above honeycomb catalyst body, the exhaust gas cannot flow into the pores, and the catalyst supported in the pores may not be able to contact the exhaust gas.

  In view of the above problems, an object of the present invention is to provide a technique that enables a large amount of catalyst to be supported and allows the supported catalyst to exhibit a catalytic action effectively.

  According to the present invention, the following honeycomb structure, honeycomb catalyst body using the honeycomb structure, and method for manufacturing the honeycomb structure are provided.

[1] A plurality of cells serving as fluid flow paths are defined and provided with a porous partition wall having a plurality of pores, the partition wall has a porosity of 45 to 70%, and the thickness of the partition wall The pore having a maximum width exceeding 10 μm in a cross section parallel to the direction is made a large pore, and the partition wall is divided into three equal parts along the thickness direction into a central region and surface layer regions on both sides of the central region. In this case, in the cross section of the surface layer region of the partition wall parallel to the thickness direction, the total area of the cross section of the large pores appearing in the cross section of the surface layer region appears in the cross section of the surface layer region. In the cross section of the central region of the partition wall, which is 60 to 100% of the total area of the cross sections of all the pores, and appears in the cross section of the central region The total area of the cross section of the large pore appears in the cross section of the central region. A honeycomb structure that is 0 to 40% of the total area of the cross-sections of all the pores.

[2] In the cross section of the partition perpendicular to the thickness direction, the shape of the outline of the pore corresponding to 20 to 100% of the total number of the pores is either a substantially circular shape or a substantially elliptical shape. The honeycomb structure according to [1].

[3] The honeycomb structure according to [1] or [2], wherein the permeability is 1 × 10 ⁻¹² to 10 × 10 ⁻¹² (m ² ).

[4] The cell density is 7.75 to 46.5 cells / cm ² , and the partition wall has a porosity of 50 to 70% and an average pore diameter of 10 to 50 μm. ] The honeycomb structure according to any one of the above.

[5] A honeycomb catalyst body comprising: the honeycomb structure according to any one of [1] to [4]; and a catalyst supported on a surface of the pore of the partition wall of the honeycomb structure.

[6] The catalyst contains at least one of a metal-substituted zeolite and vanadium and has a catalyst loading of 100 to 300 g / L, and the partition wall has a porosity (A) before loading the catalyst. The honeycomb catalyst body according to [5], wherein the porosity (B) in a state where the catalyst is supported is 0.1 to 0.6 times.

[7] A method for manufacturing a honeycomb structure for obtaining the honeycomb structure according to any one of [1] to [4], wherein the forming material includes a ceramic material and a stretchable pore former. A kneaded material preparation step for obtaining a kneaded material, a molding step for extruding the kneaded material to obtain a honeycomb molded body having partition walls for partitioning a plurality of cells, and firing the honeycomb molded body and includes a firing step to obtain a honeycomb structure, a and the pore-forming material is, der Ru method for manufacturing a honeycomb structure having a plurality of projections on the surface of the contrast porous wood.

  According to the honeycomb structure of the present invention, the honeycomb catalyst body using the honeycomb structure, and the method for manufacturing the honeycomb structure, a large percentage of pores are opened in the surface of the partition walls, and a large percentage of pores are formed in the central region. Since the width can be reduced, a large amount of catalyst can be supported in the pores of the partition walls. Furthermore, according to the honeycomb structure of the present invention, the honeycomb catalyst body using the honeycomb structure, and the method for manufacturing the honeycomb structure, the openings of the pores are not easily blocked or constricted by the catalyst. It is possible to effectively exert the catalytic action in the pores by flowing in.

1 is a perspective view schematically showing an embodiment of a honeycomb structure of the present invention. It is a schematic diagram of the A-A 'cross section in FIG. It is sectional drawing of the partition which shows the inside of the frame (alpha) in FIG. FIG. 6 is a cross-sectional view schematically showing partition walls of a conventional honeycomb structure. It is explanatory drawing at the time of implementing the purification | cleaning of exhaust gas by making the partition shown by FIG. 3 carry a catalyst. It is explanatory drawing at the time of carrying out purification | cleaning of exhaust gas by making the partition shown by FIG. 4 carry a catalyst. FIG. 3 is a schematic cross-sectional view of an example of a pore former that can be used in the method for manufacturing a honeycomb structure of the present invention. It is explanatory drawing of extrusion molding performed in one Embodiment of the manufacturing method of the honeycomb structure of this invention. It is a schematic diagram of the partition of a molded object formed by the extrusion molding shown by FIG. 8A.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the present invention.

1. Honeycomb structure:
FIG. 1 is a perspective view schematically showing an embodiment of a honeycomb structure of the present invention. As shown in the figure, the honeycomb structure 100 of the present embodiment includes a cylindrical outer peripheral wall 7 and a porous partition wall 5 that partitions the inside of the outer peripheral wall 7 into a plurality of cells 4. At both ends in the axial direction X of the honeycomb structure 100 of the present embodiment, a plurality of cells 4 are opened, and end faces 2 and 3 are formed by the edges of the outer peripheral wall 7 and the edges of the partition walls 5.

  FIG. 2 is a schematic diagram of the A-A ′ cross section in FIG. 1. As shown in the figure, in the honeycomb structure 100 of the present embodiment, a plurality of cells 4 extend along the axial direction X, and each of the cells 4 serves as a fluid flow path. it can. For example, in the honeycomb structure 100 of the present embodiment, when the gas G is allowed to flow into the cell 4 from one end face 2 (first end face), the other end face 3 (second end face) is moved along the axial direction X. ) And can be discharged to the outside.

  FIG. 3 is a cross-sectional view of the partition wall 5 schematically showing the inside of the frame α in FIG. As illustrated, since the partition walls 5 of the honeycomb structure 100 of the present embodiment are porous, a plurality of pores 10 are formed.

  In the present specification, a pore 10 having a maximum width exceeding 10 μm in a cross section of the partition wall 5 parallel to the thickness direction Y of the partition wall 5 (for example, the cross section shown in FIG. 3) is defined as a large pore 12. .

In the cross section of the partition wall 5 shown in FIG. 3, for example, the maximum width W _a of the pore 10a and the maximum width W _{b of the} pore 10b are 10 μm or more, and the maximum width W _c of the pore 10c is less than 10 μm. is there. Therefore, among the pores 10a to 10c, the pores 10a and 10b are classified as the large pore 12a and the large pore 12b, respectively.

  For example, like the large pores 12a and 12b shown in FIG. 3, in the cross section of the partition wall 5, the plurality of large pores 12 are connected by the pores 10 having a width of less than 10 μm. There is a case. In such a case, each of the connected large pores 12a and 12b is identified as one independent large pore 12. The pores 10 having a width of less than 10 μm that connect the large pores 12 are a part of the large pores 12. For example, with respect to the route R (indicated by a dotted arrow) in FIG. 3, the cell 4a facing one surface of the partition wall 5 passes through the large pore 12a, and then passes through the large pore 12b. This leads to the cell 4b facing the opposite surface of the partition wall 5. That is, the path R in FIG. 3 is composed of two large pores 12a and 12b.

  In FIG. 3, among the cross sections of the pores 10 that appear in the cross section of the partition wall 5, the cross section of the pore 10 that appears in the cross section of the central region of the partition wall 5 is indicated by “shaded”.

  In the honeycomb structure 100 of the present embodiment, the partition walls 5 parallel to the thickness direction Y when the partition walls 5 are equally divided into a central region along the thickness direction Y and surface layer regions on both sides of the central region. In the cross section of the surface layer region, the total area of the cross section of the large pore 12 appearing in the cross section of the surface layer region is 60 to 100 of the total area of the cross section of all the pores 10 appearing in the cross section of the surface layer region. %, And in the cross section of the central region of the partition wall 5 parallel to the thickness direction Y, the total area of the cross section of the large pore 12 appearing in the cross section of the central region appears in the cross section of the central region. It is 0 to 40% of the total area of the cross section of all the pores 10 that are present.

  Like the honeycomb structure 100 of the present embodiment, the total area of the cross section of the large pore 12 in the cross section of the surface layer region is 60 to 100% of the total area of the cross section of all the pores 10 in the cross section of the surface layer region. When the total area of the cross section of the large pore 12 in the cross section of the central region is 0 to 40% of the total area of the cross section of all the pores 10 in the cross section of the central region, A large proportion of the pores 10 are greatly opened, and a large proportion of the pores 10 are narrowed in the central region of the partition wall 5. Furthermore, if the flow path (for example, the path | route R which consists of the large pores 12a and 12b shown in FIG. 3) which penetrates the partition 5 by the pore 10 is formed, the said flow path will be the partition 5 Thus, the width is reduced in the central region.

  As a result, in the honeycomb structure 100 of the present embodiment, it becomes easy to allow the catalyst to enter the pores 10 in the surface region of the partition wall 5 in the step of supporting the catalyst. In addition to this, in the honeycomb structure 100 of the present embodiment, the catalyst that has entered the pores 10 in the surface layer region can be easily further penetrated into the pores 10 in the central region of the partition walls 5. Further, in the honeycomb structure 100 of the present embodiment, since the pores 10 in the central region of the partition walls 5 are narrowed, it is possible to appropriately hold the catalyst that has entered the central region of the partition walls 5. Therefore, according to the honeycomb structure 100 of the present embodiment, as shown in FIG. 5, the catalyst is applied to both the surface of the pore 10 in the surface layer region and the surface of the pore 10 in the central region of the partition wall 5. It becomes easy to carry uniformly (the description of FIG. 5 will be described later).

  Further, like the honeycomb structure 100 of the present embodiment, the total area of the cross section of the large pore 12 in the cross section of the surface layer region is 60 to 100% of the total area of the cross section of all the pores 10 in the cross section of the surface layer region. And the total area of the cross section of the large pore 12 in the cross section of the central region is 0 to 40% of the total area of the cross section of all the pores 10 in the cross section of the central region, Sufficient strength is maintained in the central region. That is, in the honeycomb structure 100 of the present embodiment, the strength of the partition walls 5 can be maintained even when the partition walls 5 have a high porosity.

  Furthermore, in the honeycomb structure 100 of the present embodiment, in the cross section of the surface layer region of the partition wall 5 parallel to the thickness direction Y, the total area of the cross section of the large pores 12 appearing in the cross section of the surface layer region is the surface layer. In the cross section of the central region of the partition wall 5 that is 60 to 90% of the total area of the cross sections of all the pores 10 appearing in the cross section of the region and parallel to the thickness direction Y, the cross section of the central region The total area of the cross-sections of the large pores 12 that appear is preferably 10 to 40% of the total area of the cross-sections of all the pores 10 that appear in the cross-section of the central region. The total area of the cross-sections of the large pores 12 appearing in is 70 to 80% of the total area of the cross-sections of all the pores 10 appearing in the cross-section of the surface layer region, and appears in the cross-section of the central region The total area of the cross section of the large pores 12 is the cross section of the central region And more preferably from 20 to 30 percent of all of the total area of the cross section of the pores 10 being.

  On the other hand, FIG. 4 schematically shows a cross-sectional view of partition walls of a conventional honeycomb structure. In FIG. 4, among the cross sections of the pores 10 that appear in the cross section of the partition wall 5, the cross section of the pore 10 that appears in the cross section of the central region of the partition wall 5 is indicated by “shaded”. In such a porous partition wall 5 of the conventional honeycomb structure, there are more large pores 12 in the center region than the surface layer region of the partition wall 5 or there is no unevenness between the surface layer region and the center region. Therefore, as shown in the figure, in the conventional honeycomb structure, the ratio of the pores 10 that are largely opened on the surface of the partition walls 5 is reduced as compared with the honeycomb structure 100 of the present embodiment described above. Therefore, in the conventional honeycomb structure, it is not easy for the catalyst to enter the pores 10 in the central region of the partition wall 5 in the step of supporting the catalyst (see FIG. 6).

  In the honeycomb structure 100 of the present embodiment, the porosity of the partition walls 5 is 45 to 70%. In addition, the porosity of a partition as used in this specification is the value measured with the mercury porosimeter. In the honeycomb structure 100 of this embodiment, when the porosity of the partition walls 5 is 45 to 70% or less, the honeycomb structure 100 is excellent in that the amount of supported catalyst can be increased while maintaining the strength of the partition walls at a predetermined level or more.

  Furthermore, in the honeycomb structure 100 of the present embodiment, the partition walls 5 preferably have a porosity of 50 to 65%, and more preferably 50 to 60%.

  In the honeycomb structure 100 of the present embodiment, in the cross section of the partition wall 5 orthogonal to the thickness direction Y, the contour shape of the pores 10 corresponding to 20 to 100% of the total number of the pores 10 is substantially circular and substantially elliptical. Preferably any of the shapes. When the cross-sectional pores 10 having substantially circular and substantially elliptical outlines exist at the above ratio, the catalyst is favorably supported on the partition walls 5. In this specification, “the shape of the outline of the pore 10 is substantially circular” means that it can be approximated to a circle when the entire outline of the cross section of one pore is viewed even if the outline is a waveform. It means a simple shape. Further, in this specification, the shape of the outline of the pore 10 is substantially elliptical. When the whole outline of the cross section of one pore is viewed even when the outline is a wavy shape, the shape is elliptical. It means an approximate shape.

Moreover, in the honeycomb structure 100 of this embodiment, it is preferable that permeability is 1 * 10 < ^-12 > ^-10 * 10 <^-12> (m < ^{2 >} ) from a viewpoint of making a communication property and favorable catalyst support. This permeability is an indicator of the passage resistance when a gas is passed through the honeycomb structure 100.

As Darcy's law, the following equation generally exists. ΔP / L = 1 / k × μ × u, ΔP [Pa]: Pressure loss during air permeation, L [m]: Sample thickness, μ [Pa · s]: Air viscosity 25 ° C., 1 atm viscosity 18.35 ⁻⁶ , u [m / s]: fluid velocity. The transmission coefficient k [m ² ] at this time is defined as permeability.

  In the honeycomb structure 100 of the present embodiment, the thickness of the partition walls 5 is not particularly limited, but is preferably 0.060 to 0.288 mm, more preferably 0.108 to 0.240 mm, It is especially preferable that it is 0.132-0.192 mm. With this configuration, the honeycomb structure 100 having high strength and reduced pressure loss can be obtained.

  The “thickness of the partition wall” referred to in this specification means a wall (partition wall 5) that partitions two adjacent cells 4 in a cross section obtained by cutting the honeycomb structure 100 perpendicularly to the cell 4 extending direction (X direction). Means the thickness of The “thickness of the partition wall” can be measured by, for example, an image analysis apparatus (trade name “NEXIV, VMR-1515” manufactured by Nikon Corporation).

In the honeycomb structure 100 of the present embodiment, the cell density is not particularly limited, it is preferable that the cell density of 15 to 140 pieces / cm ^2, further preferably from 31 to 116 pieces / cm ^2, particularly preferably 46 to 93 pieces / cm ^2. With this configuration, it is possible to suppress an increase in pressure loss while maintaining the strength of the honeycomb structure 100.

  The “cell density” referred to in this specification is the number of cells per unit area in a cross section cut perpendicularly to the cell extending direction.

In the honeycomb structure 100 of the present embodiment, the cell density is 7.75 to 46.5 cells / cm ² , and the partition walls 5 have a porosity of 50 to 70% and an average pore diameter of 10 to 50 μm. preferable. When all of the above conditions for cell density, porosity, and average pore diameter are satisfied, significant catalytic action can be exhibited when using a catalyst containing metal-substituted zeolite or vanadium. Specifically, when using a metal-substituted zeolite or vanadium-containing catalyst that expresses an amount-dependent catalytic action, a large amount of catalyst is supported on the partition walls 5 so that the quantity-dependent catalytic action is sufficiently exhibited. Can do. In addition, separation of the catalyst containing metal-substituted zeolite or vanadium from the partition walls 5 can be suppressed.

In the conventional honeycomb structure, when the cell density is 7.75 to 46.5 cells / cm ² , when a large amount of catalyst is supported on the partition wall, a large amount of catalyst is deposited on the partition wall surface. Is easy to peel. In particular, when the catalyst contains a metal-substituted zeolite, the catalyst becomes bulky, so that the tendency of the catalyst to be deposited on the partition wall surface becomes strong. Further, when the catalyst is deposited on the partition wall surface, the catalyst is more easily separated from the partition wall. According to the honeycomb structure 100 of the present embodiment, as described above, a large proportion of the pores 10 are open on the surface of the partition wall 5 and a large proportion of the pores 10 are narrowed in the central region. The catalyst is sufficiently supported up to the central region of the partition wall 5. As a result, according to the honeycomb structure 100 of the present embodiment, even if a large amount of catalyst is supported under a cell density of 7.75 to 46.5 cells / cm ² , the catalyst is peeled off from the partition walls. It becomes difficult. Moreover, in the honeycomb structure 100 of the present embodiment, even when a bulky catalyst containing a metal-substituted zeolite is used, the catalyst peeling from the partition walls can be sufficiently suppressed.

  In the honeycomb structure 100 of the present embodiment, the partition walls 5 are preferably made mainly of ceramic. Specifically, the partition wall 5 is made of silicon carbide, silicon-silicon carbide based composite material, cordierite, mullite, alumina, spinel, silicon carbide-cordierite based composite material, lithium aluminum silicate, and aluminum titanate. It is preferably at least one selected from the group. Among these, cordierite is preferable. When cordierite is used as the material for the partition walls 5, a honeycomb structure having a small thermal expansion coefficient and excellent thermal shock resistance can be obtained. In the present specification, the phrase “having ceramic as a main component” means containing 50% by mass or more of the entire ceramic.

  In the honeycomb structure 100 of the present embodiment, the shape of the cell when viewed from a cross section orthogonal to the axial direction X is not particularly limited, and other than the quadrangle shown in FIG. , Polygons such as hexagons, circles, ellipses and the like.

  In the honeycomb structure 100 of the present embodiment, the thickness of the outer peripheral wall 7 is not particularly limited, but is preferably 0.2 to 4.0 mm. In the case where the thickness of the outer peripheral wall 7 is within the above range, an increase in pressure loss when a fluid (for example, exhaust gas) is flowed into the cell 4 while maintaining the strength of the honeycomb structure 100 moderately is prevented. can do.

  In the honeycomb structure 100 of the present embodiment, the material of the outer peripheral wall 7 is preferably the same as that of the partition walls 5 but may be different.

  In the honeycomb structure 100 of the present embodiment, the shape of the outer peripheral wall 7 is not particularly limited, but in addition to the cylindrical shape shown in FIG. 1, other than that, a cylindrical shape with an elliptical bottom surface, a rectangular bottom surface, and a pentagonal shape Further, it may be a polygonal cylindrical shape such as a hexagon.

  In the honeycomb structure 100 of the present embodiment, the size of the honeycomb structure 100 is not particularly limited, but the length in the axial direction X is preferably 50 to 300 mm. Further, for example, when the honeycomb structure 100 has a cylindrical outer shape, the diameter of the bottom surface is preferably 110 to 350 mm.

2. Honeycomb catalyst body:
The honeycomb catalyst body of the present invention includes the above-described honeycomb structure of the present invention (for example, “honeycomb structure 100 of the present embodiment” described in the above section “1. Honeycomb structure”), And a catalyst supported on the surface of the pores of the partition walls.

  FIG. 5 is an explanatory view showing an embodiment of the honeycomb catalyst body of the present invention. More specifically, FIG. 5 is an explanatory diagram when the catalyst 20 is supported on the partition wall 5 shown in FIG. 3 and the exhaust gas G is purified. When the catalyst 20 is supported on the partition walls 5 in the honeycomb structure 100 described above, the ratio of the pores 10 that uniformly support the catalyst 20 on the inner wall surface increases in both the surface layer region and the central region of the partition walls 5. . That is, in the honeycomb catalyst body of the present embodiment, a large amount of catalyst 20 can be supported in the pores of the partition walls 5.

  In the honeycomb catalyst body of the present embodiment, a layer of the catalyst 20 is formed on the inner wall surface of the pore 10. Furthermore, since the honeycomb catalyst body 100 described above is used in the honeycomb catalyst body of the present embodiment, the pores 10 are small enough to allow the gas G to flow even if the catalyst 20 is supported in the pores 10. The ratio of the holes 10 still tends to be large. Therefore, as shown in FIG. 5, in the honeycomb catalyst body of the present embodiment, the gas G enters the inside of the partition wall 5 through the pores 10, and is supported by the catalyst 20 supported on the inner wall surface of the pores 10. It is possible to purify the gas G. As described above, the honeycomb catalyst body of the present embodiment can purify the gas G in the pores, so that the purification efficiency is improved as compared with the conventional honeycomb catalyst body.

Further, as shown in the figure, in the honeycomb catalyst body of the present embodiment, a large proportion of the pores 10 are greatly opened on the surface of the partition walls 5, while a large proportion of the fine pores 10 are formed in the central region of the partition walls 5. There is a tendency that the hole 10 is narrowed. Due to the shape of the pores 10, it is easy to allow the gas G to flow into the pores 10 from the cells 4 a, and when the gas G reaches the central region of the partition wall 5, it is shown in FIG. 5. as the gas G _1, it is also easy to again return to the same cell 4a. Of course, in the process in which the gas G reaches the central region of the partition wall 5 and returns to the cell 4 a again, the gas G can be purified by the catalyst 20 supported on the inner wall surface of the pore 10.

Furthermore, in the honeycomb catalyst body of the present embodiment, when the pores 10 still pass through the partition walls 5 even when the catalyst 20 is supported, the gas G reaches the center region of the partition walls 5 and is shown in FIG. as the gas G ₂ shown in, it is easy to discharge the adjacent cell 4b.

  Therefore, in the honeycomb catalyst body of the present embodiment, the catalyst 20 is supported on the inner wall surface of the pore 10 in the central region of the partition wall 5 as well as the catalyst 20 supported on the inner wall surface of the pore 10 in the surface layer region of the partition wall 5. The catalyst 20 can also be efficiently used for purifying the gas G.

  On the other hand, FIG. 6 is an explanatory view when the catalyst 20 is supported on the conventional partition wall 5 shown in FIG. 4 and the exhaust gas G is purified. In the conventional honeycomb structure, it is not easy to allow the catalyst to enter the pores 10 in the central region of the partition wall 5 in the step of supporting the catalyst. Therefore, as shown in FIG. 6, compared with the honeycomb catalyst body of the present invention (for example, one embodiment is shown in FIG. 5), pores carrying the catalyst 20 in the central region of the partition wall 5 There is a tendency that the ratio of 10 is small.

Further, in the conventional honeycomb catalyst body, since the ratio of the pores 10 that are largely open on the surface of the partition wall 5 is reduced, the gas that has flowed into the central region of the partition wall 5 as the gas G _{3 in} FIG. G ₃ tends to be difficult to return to cell 4 again. Therefore, in the conventional honeycomb catalyst body, the catalyst 20 supported in the central region of the partition wall 5 can be efficiently used for the purification of the gas G, as compared with the honeycomb catalyst body of the embodiment of the present invention described above. Have difficulty.

In the honeycomb catalyst body of the present invention, when gas flows into the cell from the inflow side end surface (one end surface), the gas is purified by the catalyst supported on the partition walls, and finally the purified gas flows out. It can be discharged from the side end surface (the other end surface). Specifically, it is possible to purify harmful substances such as carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NO _x ) contained in the gas by the catalyst supported on the partition walls. .

In particular, the honeycomb catalyst body of the present invention is preferably used for purification of exhaust gas. The exhaust gas referred to in the present specification is exhaust gas discharged from automobiles, construction machinery, industrial stationary engines, combustion equipment, and the like. Exhaust gases from these various engines and combustion equipment may contain a lot of harmful substances such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO _x ). According to the honeycomb catalyst body of the present invention, it is possible to efficiently purify harmful substances contained in exhaust gases of various engines and combustion equipment.

  In the honeycomb catalyst body of the present invention, the catalyst filling rate is preferably 50 to 90%, more preferably 60 to 80%, and particularly preferably 65 to 75%. When the filling rate of the catalyst is within the above range, there is an advantage that the contact between the catalyst and the gas is improved and the reduction of the purification rate is suppressed. Further, it is possible to prevent an increase in pressure loss when the gas flows into the honeycomb catalyst body. When the filling rate of the catalyst is not less than the lower limit value, it is possible to prevent an increase in pressure loss when the gas is introduced. Moreover, when the filling rate of the catalyst is not more than the upper limit value, there is an advantage that the catalyst is in good contact with the gas and the reduction of the purification rate can be suppressed. The catalyst filling rate referred to in this specification means “volume of catalyst filled / pore volume”.

In the honeycomb catalyst body of the present invention, the catalyst can be appropriately determined according to the purpose. Examples thereof include a three-way catalyst, an oxidation catalyst, a NO _X selective reduction catalyst, and a NO _X storage reduction catalyst. The amount of catalyst supported per unit volume of the honeycomb catalyst body is preferably 100 to 300 g / L, more preferably 150 to 250 g / L (where L is liter).

A three-way catalyst refers to a catalyst that mainly purifies hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO _x ). For example, a catalyst containing platinum (Pt), palladium (Pd), and rhodium (Rh) can be given.

  Examples of the oxidation catalyst include those containing a noble metal. Specifically, those containing at least one selected from the group consisting of platinum, palladium, and rhodium are preferable.

Examples of the NO _X selective reduction catalyst include those containing at least one selected from the group consisting of metal-substituted zeolite, vanadium, titania, tungsten oxide, silver, and alumina.

  In the honeycomb catalyst body of the present invention, when the catalyst contains at least one of metal-substituted zeolite and vanadium, the amount of catalyst supported is improved from the viewpoint of sufficiently increasing the contact frequency between the catalyst and the gas and improving the purification efficiency. Is 100 to 300 g / L, and the partition wall has a porosity (B) of 0.1 to 0.6 times in a state where the catalyst is supported relative to the porosity (A) before the catalyst is supported [ In other words, porosity (B) / porosity (A) = 0.1 to 0.6] is preferable.

Furthermore, in the honeycomb catalyst body of the present invention, when the catalyst contains at least one of metal-substituted zeolite and vanadium, the catalyst loading is 100 to 300 g / L, and the partition walls have a porosity of 50 to 70. % And the average pore diameter of 10 to 50 μm and the porosity (B) in a state where the catalyst is supported relative to the porosity (A) before the catalyst is supported are 0.1 to 0.6 times, Further, the cell density is preferably 7.75 to 46.5 cells / cm ² (50 to 300 cpsi). When all of the above catalyst loading, porosity (B) / porosity (A) value, and cell density conditions are satisfied, the contact frequency between the catalyst and the gas is sufficiently increased to improve the purification efficiency, and It is possible to suppress an increase in pressure loss and to prevent the catalyst from peeling from the partition wall.

Examples of the NO _X storage reduction catalyst include alkali metals and / or alkaline earth metals. Examples of the alkali metal include potassium, sodium, and lithium. Examples of the alkaline earth metal include calcium.

3. Manufacturing method of honeycomb structure:
The honeycomb structure of the present invention can be obtained, for example, by the following manufacturing method (the manufacturing method of the honeycomb structure of the present invention). The method for manufacturing a honeycomb structure of the present invention includes a clay preparation step, a forming step, and a firing step. The clay preparation step is a step in which a ceramic raw material and a forming raw material containing a pore former are mixed and kneaded to obtain a clay. The forming step is a step of obtaining a honeycomb formed body in which a plurality of cells are formed by extruding the clay obtained in the clay preparation step into a honeycomb shape. The firing step is a step of firing the honeycomb formed body to obtain a honeycomb structure. According to the method for manufacturing a honeycomb structure of the present invention, which will be described in detail below, the above-described honeycomb structure of the present invention can be favorably manufactured.

  One embodiment of the method for manufacturing a honeycomb structure of the present invention will be specifically described below.

3-1. Clay preparation process:
In the clay preparation step of the method for manufacturing a honeycomb structure of the present embodiment, a ceramic raw material and a forming raw material containing a pore former are mixed and kneaded to obtain a clay. And in the clay preparation process in the manufacturing method of the honeycomb structure of the present embodiment, a material made of a stretchable material is used as the pore former. In the method for manufacturing a honeycomb structure of the present embodiment, the above-described honeycomb structure can be efficiently manufactured by using a pore-forming material having stretchability.

  That is, in the method for manufacturing a honeycomb structure of the present embodiment, by using a stretchable pore former, the porosity is 45 to 70%, and “the cross section of the surface layer region of the partition wall is the cross section of the surface layer region. The total area of the cross-sections of the large pores appearing in Fig. 5 is 60 to 100% of the total area of the cross-sections of all the pores appearing in the cross-section of the surface layer region, and the central region of the partition wall parallel to the thickness , The total area of the cross-sections of the large pores appearing in the cross-section of the central region is 0 to 40% of the total area of the cross-sections of all the pores appearing in the cross-section of the central region. It is possible to efficiently form partition walls having a pore distribution state (hereinafter referred to as “large pore distribution state A” for convenience of explanation).

  As a pore former that can be used in the method for manufacturing a honeycomb structure of the present embodiment, in particular, it is excellent in stretchability and easy to make partition walls having a large pore distribution state A. Polymers are preferred.

  In the method for manufacturing a honeycomb structure of the present embodiment, the average particle diameter of the pore former is preferably 50 to 200 μm. When the average particle diameter of the pore former is 50 to 200 μm, the partition walls of the finally obtained honeycomb structure can have sufficient strength, and the efficiency of filling the catalyst into the pores of the partition walls can be increased. Is possible. Furthermore, in the manufacturing method of the honeycomb structure of the present embodiment, the thickness is more preferably 80 to 170 μm, and particularly preferably 100 to 150 μm.

Furthermore, in the manufacturing method of the honeycomb structure of the present embodiment, the pore former, by the pore former having a Der Ru (plurality of protrusions having a plurality of projections on its surface, the distribution of large pore An example of a mechanism for producing a partition including A will be described later).

  FIG. 7 is a cross-sectional view of an example of a pore former 200 having a plurality of protrusions 250 that can be used in the method for manufacturing a honeycomb structure of the present embodiment. The pore former 200 having a plurality of protrusions 250 is integrally formed of a stretchable material (for example, foamed resin, water-absorbing polymer) having a plurality of protrusion shapes (protrusion 250). May be used.

  In addition, for the pore former having a plurality of protrusions, the pore former (I) having a substantially spherical shape has a stretchability with an average particle diameter smaller than that of the pore former (I). You may use what was made by adhere | attaching material (II). Here, the average particle diameter of the pore former (II) is 1 / of the average particle diameter of the pore former (I) from the viewpoint that it is possible to more reliably produce the partition wall having the large pore distribution state A. It is preferable that it is 40-1 / 7.

  Further, in the method for manufacturing a honeycomb structure of the present embodiment, a pore former having a plurality of protrusions is used, and the pore former is made from the pore former (I) and the pore former (II). The average particle diameter of the pore former (II) is 1/40 to 1/7 of the average particle diameter of the pore former (I), and on the surface of one particle of the pore former (I). More preferably, the pore former (II) is made by adhering 5 to 20 particles. When the conditions for the average particle diameter of the pore former (II) and the number of the pore former (II) particles adhered to the surface of one particle of the pore former (I) are satisfied, A partition provided with the distribution state A can be more reliably manufactured.

  As used herein, the average particle diameter of the pore former means an average particle diameter classified by sieving (expressed by a test sieve opening measured by a sieving method).

  In the method for manufacturing a honeycomb structure of the present embodiment, the average particle diameter of the pore former is preferably 50 to 200 μm. When the average particle diameter of the pore former is 50 to 200 μm, the partition walls of the finally obtained honeycomb structure can have sufficient strength, and the efficiency of filling the catalyst into the pores of the partition walls can be increased. Is possible. Furthermore, in the method for manufacturing a honeycomb structured body of the present embodiment, the average particle diameter of the pore former is more preferably 80 to 170 μm, and particularly preferably 100 to 150 μm.

  In the method for manufacturing a honeycomb structure of the present embodiment, a pore former having a plurality of protrusions is used, and the pore former is made of the pore former (I) and the pore former (II). The average particle diameter of the pore former (I) is preferably 30 to 180 μm, and the average particle diameter of the pore former (II) is preferably 2 to 20 μm. When the average particle diameter of the pore former (I) and the pore former (II) satisfies the above conditions, the partition wall of the honeycomb structure finally obtained can have sufficient strength, and the pores of the partition wall It is possible to increase the efficiency of filling the catalyst inside. Furthermore, in the manufacturing method of the honeycomb structure of the present embodiment, the average particle diameter of the pore former (I) is 60 to 150 μm, and the average particle diameter of the pore former (II) is 2 to 17 μm. Is more preferable. In particular, in the method for manufacturing a honeycomb structure of the present embodiment, the average particle diameter of the pore former (I) is 80 to 130 μm, and the average particle diameter of the pore former (II) is 5 to 15 μm. Is most preferred.

  In the manufacturing method of the honeycomb structure of the present embodiment, the content of the pore former in the forming raw material is usually 1 to 10 parts by mass and 1 to 8 parts by mass with respect to 100 parts by mass of the ceramic raw material. It is preferably 1 to 6 parts by mass. If the amount of pore former added is less than 1 part by mass, the number of large pores formed in the partition walls may be reduced, and the amount of catalyst that can be supported on the resulting honeycomb structure may be reduced. On the other hand, when the added amount of the pore former exceeds 10 parts by mass, large pores are excessively formed in the partition walls, and as a result, the strength of the resulting honeycomb structure may be lowered.

  Examples of the ceramic raw material that can be used in the method for manufacturing a honeycomb structure of the present embodiment include silicon carbide, silicon-silicon carbide based composite material, cordierite forming raw material, mullite, alumina, spinel, silicon carbide cordierite based composite material, lithium It is preferably at least one selected from the group consisting of aluminum silicate and aluminum titanate. Among the ceramic raw materials listed here, cordierite forming raw materials are preferable. This is because when a cordierite forming raw material is used, a honeycomb structure having a small thermal expansion coefficient and excellent thermal shock resistance can be obtained.

  In the method for manufacturing a honeycomb structure of the present embodiment, the forming raw material may include a dispersion medium, an additive, and the like in addition to the ceramic raw material and the pore former.

  Examples of the dispersion medium that can be used in the method for manufacturing a honeycomb structure of the present embodiment include water. Examples of the additive include an organic binder and a surfactant. It is preferable that content of a dispersion medium is 30-150 mass parts with respect to 100 mass parts of ceramic raw materials.

  Examples of the organic binder that can be used in the method for manufacturing a honeycomb structure of the present embodiment include methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. It is preferable that content of an organic binder is 1-10 mass parts with respect to 100 mass parts of ceramic raw materials.

  As a surfactant that can be used in the method for manufacturing a honeycomb structure of the present embodiment, ethylene glycol, dextrin, fatty acid soap, polyalcohol, or the like can be used. These surfactants may be used individually by 1 type, and may be used in combination of 2 or more type. It is preferable that content of surfactant is 0.1-5.0 mass parts with respect to 100 mass parts of ceramic raw materials.

  In the method for manufacturing a honeycomb structure of the present embodiment, the method for kneading the forming raw material to form the kneaded material is not particularly limited, and examples thereof include a method using a kneader, a vacuum kneader, or the like.

3-2. Molding process:
In the forming step of the manufacturing method of the honeycomb structure of the present embodiment, the clay obtained in the clay preparation step is extruded into a honeycomb shape to obtain a honeycomb formed body. In this honeycomb formed body, a plurality of cells penetrating the honeycomb formed body are formed. Extrusion can be performed using a die having a desired cell shape, partition wall thickness, and cell density. As the material of the die, a cemented carbide which does not easily wear is preferable.

  Next, the forming process of the manufacturing method of the honeycomb structure of the present embodiment will be described in detail by taking as an example the case of extrusion molding using the pore former 200 shown in FIG.

  FIG. 8A is an explanatory diagram of extrusion molding in the method for manufacturing a honeycomb structure of the present embodiment. In the extrusion molding described here, a die having thin grooves (slits) cut in a lattice shape is used. The clay 150 that has passed through the slit of the die forms the partition wall 170 of the honeycomb formed body.

  Furthermore, in the method for manufacturing a honeycomb structure according to the present embodiment, as shown in FIG. 7, the pore-forming material 200 made of a stretchable material and having a plurality of protrusions 250 is used. In such a pore former 200, when an external force that crushes the pore former 200 is applied, first, there is a tendency to deform and contract from the protrusion 250.

  Therefore, in the method for manufacturing a honeycomb structure according to the present embodiment, as shown in FIG. 8A, when the pore former 200 included in the clay 150 is unevenly distributed near the wall surface 400 of the base slit. In the pore former 200, the protrusions 250 are mainly crushed and deformed by the wall surface 400 of the slit. For this reason, in the method for manufacturing a honeycomb structure of the present embodiment, the position of the pore former 200 (position at the center of the pore former 200) is kept unevenly distributed near the wall surface 400 of the slit. For example, the protrusion 250a shown in FIG. 8A is in a state of being crushed and deformed by the wall surface 400 of the slit, and the protrusion 250b shown in FIG. It is in a state of being crushed and deformed by the pore former 200. Thus, in the method for manufacturing a honeycomb structure of the present embodiment, the clay 150 can be passed through the slit while the pore former 200 is unevenly distributed.

  FIG. 8B is a schematic diagram of a cross section of a partition wall of a honeycomb formed body formed by extrusion molding shown in FIG. 8A. When the partition wall 170 of the honeycomb formed body is formed according to the embodiment shown in FIG. 8A, a large number of pore formers 200 can be unevenly distributed in the surface layer region of the partition wall 170 as shown in FIG. 8B. . Reflecting the uneven distribution of the pore former 200, the partition walls of the honeycomb structure finally obtained also have a large number of large pores unevenly distributed in the surface layer region of the partition walls as shown in FIG. I can do it.

3-3. Firing process:
In the firing step of the honeycomb structure manufacturing method of the present embodiment, the honeycomb formed body obtained in the above-described forming step is fired to obtain the honeycomb structure. The honeycomb structure obtained in this manner is provided with a porous partition wall in which a plurality of cells serving as fluid flow paths are partitioned and a plurality of pores are formed.

  In the firing step of the manufacturing method of the honeycomb structure of the present embodiment, the firing temperature can be appropriately determined depending on the material of the honeycomb formed body. For example, when the material of the honeycomb formed body is cordierite, the firing temperature is preferably 1380 to 1450 ° C, and more preferably 1400 to 1440 ° C. The firing time is preferably about 3 to 10 hours.

  In the method for manufacturing a honeycomb structured body of the present embodiment, the honeycomb formed body may be dried before firing. The drying method is not particularly limited, and examples thereof include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. Among these, it is preferable to perform dielectric drying, microwave drying, or hot air drying alone or in combination. The drying conditions are preferably a drying temperature of 30 to 150 ° C. and a drying time of 1 minute to 2 hours.

4). Manufacturing method of honeycomb catalyst body:
The honeycomb catalyst body of the present invention can be manufactured, for example, as follows.

  First, a honeycomb structure is produced as a catalyst carrier. This honeycomb structure can be manufactured according to the above-described method for manufacturing a honeycomb structure of the present invention.

  Next, a catalyst slurry is prepared. The average particle diameter of the catalyst contained in the catalyst slurry is 0.5 to 5 μm. Furthermore, the viscosity (25 degreeC) of a catalyst slurry is 1-10 mPa * s. When both the average particle diameter and the viscosity of the catalyst are equal to or more than the lower limit values, it is possible to prevent the catalyst from being excessively filled in the pores, and the obtained honeycomb touch It is possible to suppress an increase in pressure loss in the medium. When both the average particle diameter and the viscosity of the catalyst are not more than the upper limit values, the catalyst can be surely filled into the pores. Therefore, it becomes easy to obtain a honeycomb catalyst body with high exhaust gas purification performance.

  Next, the catalyst slurry is supported on the honeycomb structure. As a method of supporting the catalyst slurry on the honeycomb structure, a conventionally known method such as dipping or suction can be employed. In addition, after performing dipping or suction, excess catalyst slurry may be blown off with compressed air.

  Next, the honeycomb structure carrying the catalyst slurry is dried and fired. In this way, a honeycomb catalyst body can be manufactured. Drying conditions can be 120 to 180 ° C. and 10 to 30 minutes. Firing conditions can be 550 to 650 ° C. and 1 to 5 hours.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

Example 1
[Preparation of pore former]
A foamed resin pore-forming material (II) having an average particle size smaller than that of the pore-forming material (I) is bonded to the foamed resin-made pore-forming material (I), thereby forming a plurality of protrusions. A pore material was produced. Specifically, after applying an adhesive to the surface of the pore former (II) in advance, it is added to the container containing the pore former (I), thereby forming the pore former (I) and the pore former (I). The pore former (II) was mixed and the pore former (II) was adhered to the surface of the pore former (I). In addition, after performing the process to make it adhere | attach, it was confirmed that the pore making material which has a some protrusion part was produced by taking out a pore making material and observing using an optical microscope. The average particle diameter of the pore former (I), the average particle diameter (μm) of the pore former (II), and the pore former when the pore former (II) is mixed and bonded to the pore former (I) The value of the ratio of the number of pore former (II) to the number of (I) [number of pore former (II) / number of pore former (I)] is shown in Table 1.

[Preparation of honeycomb structure]
As the cordierite forming raw material, alumina, aluminum hydroxide, kaolin, talc, and silica were used. 100 parts by mass of the cordierite forming material, 5 parts by mass of the pore former having the plurality of protrusions described above, 85 parts by mass of water (dispersion medium), 8 parts by mass of water-absorbing hydroxypropylmethylcellulose (organic binder), and surfactant 3 parts by weight were added. Thereafter, mixing and further kneading were performed to obtain a clay.

  Next, the kneaded material was extruded using a predetermined mold to obtain a honeycomb formed body. In the honeycomb formed body, square cells were formed in a cross section perpendicular to the cell extending direction, and the overall shape was a columnar shape. The obtained honeycomb formed body was dried with a microwave dryer. Thereafter, it was further completely dried with a hot air dryer. Subsequently, both end faces of the dried honeycomb formed body were cut and adjusted to predetermined dimensions.

  The honeycomb formed body thus obtained was further fired at 1410 to 1440 ° C. for 5 hours to obtain a honeycomb structure.

The obtained honeycomb structure had a diameter of 266.7 mm and a length in the central axis direction of 152.4 mm. The partition wall thickness was 165.1 μm, and the cell density was 62.0 cells / cm ² .

[Preparation of honeycomb catalyst body]
1 kg of water was added to 200 g of β-zeolite (copper ion exchanged zeolite) having an average particle diameter of 5 μm, and wet pulverized by a ball mill. As a binder, 20 g of alumina sol was added to the obtained crushed particles to obtain a catalyst slurry. This catalyst slurry was prepared to have a viscosity of 5 mPa · s. The honeycomb structure was immersed in this catalyst slurry. Then, it dried at 120 degreeC for 20 minutes, and baked at 600 degreeC for 1 hour. Thus, a honeycomb catalyst body was obtained. The catalyst loading on the honeycomb catalyst body was found to be 250 g / liter.

(Examples 2 to 14)
In Examples 2 to 14, the average particle diameter (μm) of the pore former (I), the average particle diameter (μm) of the pore former (II), and the pore former (I) shown in Table 1 The value of the ratio of the number of pore formers (II) to the number of pore formers (I) when the pore former (II) is mixed and bonded to [the number of pore formers (II) / the pore former ( In the number of I)], a honeycomb structure and a honeycomb contact were produced in the same manner as in Example 1 except that a pore former having a plurality of protrusions was prepared and the pore former thus obtained was used. A medium was made.

(Comparative Examples 1-3)
In Comparative Examples 1 to 3, the honeycomb structure was produced in the same manner as in Example 1 except that the average particle diameter (μm) shown in Table 2 was used as a substantially spherical carbon powder pore former. And honeycomb catalyst bodies were prepared.

(Examples 15 to 19)
In Examples 15 to 19, the average particle diameter (μm) of the pore former (I), the average particle diameter (μm) of the pore former (II), and the pore former (I) shown in Table 3 The value of the ratio of the number of pore formers (II) to the number of pore formers (I) when the pore former (II) is mixed and bonded to [the number of pore formers (II) / the pore former ( A honeycomb structure and a honeycomb catalyst body were manufactured in the same manner as in Example 1 except that a pore former having a plurality of protrusions was prepared in the number of I)], and this was used. In all of Examples 15 to 19, the average pore diameter was 23 μm, the proportion of large pores in the surface layer region was 72%, and the proportion of large pores in the central region was 25%.

(Examples 20 to 26)
In Examples 20 to 26, as shown in Table 3, the average particle diameter (μm) of the pore former (I), the average particle diameter (μm) of the pore former (II), and the pore former (I) The value of the ratio of the number of pore formers (II) to the number of pore formers (I) when the pore former (II) is mixed and bonded to [the number of pore formers (II) / the pore former ( The number of I)] was used to prepare a pore former having a plurality of protrusions, and this was used except that vanadium was used instead of β-zeolite (copper ion exchanged zeolite) when preparing the catalyst slurry. A honeycomb structure and a honeycomb catalyst body were produced by the same method as in Example 1. In all of Examples 20 to 26, the average pore diameter was 23 μm, the proportion of large pores in the surface layer region was 72%, and the proportion of large pores in the central region was 25%.

(Comparative Examples 4-6)
The average particle size (μm) shown in Table 3 is used as a pore-forming material of a substantially spherical carbon powder, and in addition to the cell density shown in Table 5, by the same method as in Comparative Example 1, A honeycomb structure and a honeycomb catalyst body were produced. In Comparative Examples 4 to 6, the proportion of large pores in the surface layer region was 50% to 71%, and the proportion of large pores in the central region was 26% to 42%. In Comparative Examples 4 to 6, the porosity (A) was 35% or less (out of the range of 45 to 70%).

  For the honeycomb structures of Examples 1 to 26 and Comparative Examples 1 to 6, [Porosity (A)], [Average pore diameter], [Measurement of ratio of large pores], and [Measurement of permeability] Evaluation was performed (results are shown in Table 4 or Table 5). The evaluation method for each evaluation is shown below. In each evaluation, evaluation is performed in three stages of “A”, “B”, and “C”. “A” and “B” are acceptable. “A” means superior to “B”. “C” is rejected.

[Porosity (A) (%)]:
The porosity (A) (%) in the honeycomb structure was measured by a mercury porosimeter (mercury intrusion method). As the mercury porosimeter, the product name: Auto Pore III Model 9405 manufactured by Micromeritics was used.

[Average pore diameter (μm)]:
The average pore diameter of the partition walls was measured by a mercury porosimeter (mercury intrusion method).

[Measurement of proportion of large pores]:
Using a scanning electron microscope (SEM), the cross section perpendicular to the cell extending direction of the honeycomb partition walls was arbitrarily photographed in four fields of view. The shooting magnification is 100 times. One field of view was 640 vertical by 480 horizontal pixels and 1 pixel = 1 μm. The photographed image was binarized by image analysis (“WINROOF” manufactured by Mitani Corporation). After binarization, the area ratio of the pores was calculated.

[Measurement of permeability]
As Darcy's law, the following equation generally exists. ΔP / L = 1 / k × μ × u, ΔP [Pa]: Pressure loss during air permeation, L [m]: Sample thickness, μ [Pa · s]: Air viscosity 25 ° C., 1 atm viscosity 18.35 ⁻⁶ , u [m / s]: fluid velocity. The transmission coefficient k [m ² ] at this time was defined as permeability and calculated.

  The honeycomb catalyst bodies of Examples 1 to 26 and Comparative Examples 1 to 6 were evaluated for [porosity (B)], [purification efficiency], [pressure loss], [thermal shock resistance], and [catalyst peeling]. (The results are shown in Table 4 or Table 5). The evaluation method for each evaluation is shown below. In each evaluation, evaluation is performed in three stages of “A”, “B”, and “C”. “A” and “B” are acceptable. “A” means superior to “B”. “C” is rejected.

[Porosity (B) (%)]:
The porosity (B) (%) in the honeycomb catalyst body was measured by the same method as the above-described porosity (A). Furthermore, the ratio of the porosity (B) to the porosity (A) [porosity (B) / porosity (A)] was calculated.

[Purification efficiency (NO _x purification efficiency)]
First, the honeycomb catalyst body and flushed with test gas containing NO _X. Thereafter, the NO _x amount of the exhaust gas discharged from the honeycomb catalyst body was analyzed with a gas analyzer.

Here, the temperature of the test gas flowing into the honeycomb catalyst body was set to 200 ° C. The temperature of the honeycomb catalyst body and the test gas was adjusted with a heater. An infrared image furnace was used as the heater. As the test gas, a gas in which 5% by volume of carbon dioxide, 14% by volume of oxygen, 350 ppm of nitrogen monoxide (volume basis), 350 ppm of ammonia (volume basis) and 10% by volume of water were mixed with nitrogen. As the test gas, water and a mixed gas obtained by mixing other gases (nitrogen, carbon dioxide, oxygen, nitric oxide, ammonia) were prepared separately. And when performing a test, these were mixed in piping and the gas for a test was obtained. As the gas analyzer, “MEXA9100EGR manufactured by HORIBA” was used. The space velocity when the test gas flows into the honeycomb catalyst body was set to 50000 (time- ¹ ).

Table 4 "NO _X purification rate" in from _the amount of NO _X in the test gas, the value obtained by subtracting the amount of NO _X in the exhaust gas from the honeycomb catalyst body, divided by the amount of NO _X in the test gas, 100 It is a doubled value. Here, "A" when NO _X purification rate is 50% or more, when less than 30% ultra and 50% was evaluated as "B", "C" when 30% or less.

[Pressure loss]
Air was circulated through the honeycomb catalyst body at a flow rate of 0.5 m ³ / min at room temperature. In this state, the difference between the pressure on the air inflow side and the pressure on the air outflow side was measured. This pressure difference was calculated as a pressure loss. When the pressure loss ratio is less than 1.15, it is “A”, when it is 1.15 or more and less than 1.20, it is “B”, and when it is 1.20 or more, it is “C”.

[Strength]
The strength of the honeycomb catalyst body was measured. The measurement of strength was performed based on an isostatic fracture strength test defined in an automobile standard (JASO standard) M505-87 issued by the Japan Society for Automotive Engineers. The isostatic fracture strength test is a test in which a honeycomb catalyst body is placed in a rubber cylindrical container, covered with an aluminum plate, and isotropically compressed in water. That is, the isostatic fracture strength test is a test that simulates the load of compression load when the honeycomb catalyst body is gripped on the outer peripheral surface of the converter can body. The isostatic fracture strength is indicated by a pressurized pressure value (MPa) when the honeycomb catalyst body is destroyed. “A” when the pressure value (MPa) is 2.00 MPa or more, “B” when it is 0.9 MPa or more and less than 2.0 MPa, “C” when it is less than 0.9 MPa. "

[Thermal shock resistance]
First, the honeycomb catalyst body was carried into a furnace having a predetermined temperature, and the honeycomb catalyst body was left at the same temperature for 60 minutes. After 60 minutes, the honeycomb catalyst body was taken out from the furnace and moved to a room temperature, and it was confirmed whether or not the end face of the honeycomb catalyst body had cracks. “A” when the temperature in the furnace at the start of cracking is 550 ° C. or more, “B” when 500 ° C. or more and less than 550 ° C., and when it is less than 500 ° C. “C”.

[Catalyst peeling test]
The honeycomb catalyst body was packaged in a sheet metal container, an inlet exhaust temperature of 650 ° C. and a 30 G excitation force were applied, and a durability test for 100 hours was performed. The weight of the honeycomb catalyst body before and after the durability test was measured, and the decrease in the weight of the honeycomb catalyst body was measured as the catalyst peeling amount. When the weight reduction of the honeycomb catalyst body is less than 3%, “A” is set, and when it is 3% or more and less than 5%, “B” is set, and when it is 5% or more, “C” is set.

In the honeycomb catalyst bodies of Examples 1 to 14, the evaluations of “NO _X purification rate”, “pressure loss”, “strength”, and “thermal shock resistance” are all “A” or “B”, that is, “pass”. there were. On the other hand, in the honeycomb catalyst bodies of Comparative Examples 1 to 3, at least one of the above four evaluations was “C” (failed).

In the honeycomb catalyst bodies of Examples 15 to 26, the evaluations of “NO _X purification rate”, “pressure loss”, and “catalyst peeling” were all “A” or “B”, that is, “pass”. On the other hand, in the honeycomb catalyst bodies of Comparative Examples 4 to 6, the evaluation of “catalyst peeling” was “C” (failed).

  INDUSTRIAL APPLICABILITY The present invention can be used as a honeycomb structure that supports a catalyst for exhaust gas purification, a honeycomb catalyst body using the honeycomb structure, and a method for manufacturing the honeycomb structure.

2: (one) end face, 3: (other) end face, 4, 4a, 4b: cell, 5: partition wall, 7: outer peripheral wall, 10, 10a to 10c: pore, 12, 12a, 12b: fine Pores, 20: catalyst, 30: pore openings (closed by catalyst), 100: honeycomb structure, 150: clay, 170: partition walls made from clay, 200: pore former, 250, 250a , 250b: protrusion, 270: surface (of the pore former), 400: wall surface (of the slit of the nozzle), 450: inlet of (the slit), G, G _{1 to} G ₃ : gas.

Claims (7)

A plurality of cells serving as fluid flow paths are defined, and a porous partition wall having a plurality of pores is provided.
The partition wall has a porosity of 45 to 70%;
In the cross section parallel to the thickness direction of the partition wall, the pore having a maximum width exceeding 10 μm is a large pore, and the partition wall has a central region along the thickness direction and surface layer regions on both sides of the central region. In the cross section of the surface layer region of the partition wall parallel to the thickness direction, the total area of the cross section of the large pores appearing in the cross section of the surface layer region is equal to the surface layer region. In the cross section of the central region of the partition wall that is 60 to 100% of the total area of the cross sections of all the pores appearing in the cross section and is parallel to the thickness direction, the cross section of the central region A honeycomb structure in which the total area of the cross-sections of the large pores appearing in 1 is 0 to 40% of the total area of the cross-sections of all the pores appearing in the cross-section of the central region.   The cross-section of the partition perpendicular to the thickness direction has a shape of the outline of the pore corresponding to 20 to 100% of the total number of the pores, which is either a substantially circular shape or a substantially elliptical shape. The honeycomb structure described. Permeability is ^{1 × 10 -12 ~10 × 10 -12} (m 2) a honeycomb structure according to claim 1 or 2. The cell density is 7.75-46.5 cells / cm ² ,
The honeycomb structure according to any one of claims 1 to 3, wherein the partition walls have a porosity of 50 to 70% and an average pore diameter of 10 to 50 µm. A honeycomb structure according to any one of claims 1 to 4,
And a catalyst supported on the surface of the pores of the partition walls of the honeycomb structure. The catalyst contains at least one of a metal-substituted zeolite and vanadium and has a catalyst loading of 100 to 300 g / L,
6. The partition wall according to claim 5, wherein the porosity (B) in a state where the catalyst is supported is 0.1 to 0.6 times the porosity (A) before the catalyst is supported. Honeycomb catalyst body. A method for manufacturing a honeycomb structure for obtaining the honeycomb structure according to any one of claims 1 to 4,
A clay preparation step in which a molding raw material containing a ceramic raw material and a stretchable pore former is mixed and kneaded to obtain a clay;
A molding step of extruding the kneaded material to obtain a honeycomb molded body having partition walls for partitioning a plurality of cells;
A firing step of firing the honeycomb formed body to obtain a honeycomb structure ,
The pore-forming material is, der Ru method for manufacturing a honeycomb structure having a plurality of projections on the surface of the contrast porous wood.

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